DESCRIPTION: This project investigates the dynamics of plasticity in auditory cortex. While reorganization of the frequency map in primary auditory cortex has been fully established in earlier studies, how these changes occur is unknown. Cortical reorganization has been revealed mainly through cortical frequency maps derived from making many penetrations with a single electrode in an acute preparation, but these recordings cannot measure functional connectivity. The complex anatomical structure of primary auditory cortex, which includes extensive thalamocortical inputs, intrinsic circuits, and varied cellular morphology, suggests that functional connectivity is an important component of the cortex. Knowing the dynamics of cortical reorganization and the associated changes in functional connectivity will provide insight into the underlying mechanisms of cortical plasticity. This project will further the understanding of cortical plasticity and its relation to learning and frequency-specific hearing loss. The simultaneous spike-discharge activity of many units distributed throughout auditory cortex will be recorded chronically over several months to allow, for the first time, continuous measurement of the cortical frequency map and functional connectivity as the animal learns new tasks or adapts to restricted sensory inputs. This approach will be combined with experimental procedures that have been shown to induce frequency map reorganization in Al in order to directly measure the dynamics of auditory cortex plasticity. The outcome of this research will be a quantitative picture of auditory cortex plasticity expressed by changes in tuning and functional connectivity over time. Auditory cortex plasticity is one example of the plasticity that takes place throughout the CNS and is thought to be a substrate for learning in general. The cortical organization observed in awake cats will lead to new insight into the types of neural plasticity that may take place in adult humans that suffer a severe hearing loss. It will also ultimately contribute to the understanding of the effects of hearing aids and cochlear prostheses.